Regenerative burners are commonly used in molten aluminum, steel reheat, forging and glass furnaces. Regenerative burners typically include a pair of independently functioning burner units connected by a system of valves which allow each unit to alternately function as a burner and as a flue for the other unit when functioning as a burner. Cycle times between burner and flue functions may be as short as 30 seconds or so. The advantage of regenerative burners is that one unit captures the heat of the escaping flue gas of the other burner and uses the captured heat to warm a bed of thermal media which in turn pre-heats incoming combustion air, thus reducing fuel consumption as well as emissions.
However, as the burner units typically reach temperatures of 1500 degrees Fahrenheit of more during routine operation, and the incoming air is typically at ambient temperature, the rapid cycling of the bed media makes thermal shock damage to the media problematic. Further, heat recovery from the media is a function of the heat transfer, heat capacity, and effective surface area of the media. It is therefore advantageous for bed media to transfer heat quickly and efficiently to and from the surrounding gasses to minimize thermal shock as well as to most efficiently use the heat of flue gas to preheat incoming air.
The media size and shape also directly impact the pressure drop or resistance to gas flow through the media bed. Orientation of the media, shape, surface area, and void fractions all impact the pressure drop.
Another problem with standard spherical bed media is the rapid build-up of contamination on the surface of the media. Contaminants of the media from the flue gas, from the melting of painted metals and the like, build up on the media surfaces and interfere with their ability to efficiently transfer heat, reduce air flow and increase pressure drop thus requiring frequent cleaning and change-outs of the bed media.
Thus, there is a need for inexpensive heat exchange media having good thermal mass, heat transfer properties, and mechanical stability that will not contribute excessively to pressure drop. The present novel technology addresses this need.